1. Field of the Invention
The present invention relates to a magnetic recording medium such as a magnetic tape and a magnetic disc which have a non-magnetic layer and a magnetic layer more particularly, to a magnetic recording medium having a non-magnetic layer and a magnetic layer which contain a particular compound so as to obtain an excellent abrasion resistance, running condition, and durability.
2. Description of the Prior Art
In a so-called coating-type magnetic medium having one or more than one magnetic layers formed by applying a magnetic coating mainly consisting of a very fine magnetic powder and a resin binder, in order to obtain a high recording density, the magnetic layer is made as a thin film so as to obtain an excellent electro-magnetic conversion characteristic especially in a short-wavelength band. It should be noted that such a thin film also reduces a self-demagnetization loss during a recording and a thickness loss during a reproduction.
However, if the magnetic layer is made as a thin film of 2 .mu.m or below, the surface configuration of the non-magnetic support body affects the surface configuration of the magnetic layer, deteriorating the electro-magnetic conversion characteristic as well as causing a drop-out. To cope with this, between the non-magnetic support body and the magnetic layer, there is formed a non-magnetic layer having at least a non-magnetic powder dispersed in a binding material.
In the magnetic recording medium having such a configuration, it is possible to obtain an excellent electro-magnetic conversion characteristic in a short-wavelength and, because of the thinness of the magnetic layer, to reduce a self-demagnetization loss during a recording and a thickness loss during a reproduction. Furthermore, the thin magnetic layer also enables to reduce production costs.
However, if the magnetic layer is made as a thin film, the magnetic layer serving as the upper most layer can contain only a limited quantity of lubricant and abrasives and the friction coefficient is increased, which in turn deteriorates the abrasion resistance, running condition, and durability. Furthermore, the magnetic layer serving as the upper most layer should contain a ferromagnetic powder of a very small particle size, which lowers the film strength of the magnetic as well as deteriorates the running condition and durability because the magnetic layer has a more flat and smoothed surface.
To cope with this, it has been suggested to suppress the friction coefficient by containing various lubricants in the magnetic layer serving as the uppermost layer of the magnetic recording medium or forming a top coat layer of various lubricants coated on the aforementioned magnetic layer. As such lubricants, there can be exemplified higher fatty acid, its ester, paraffin, silicone, and the like. Especially, fatty acid is said to effectively suppress the friction.
However, even if such lubricants are used, it becomes difficult to sufficiently lower the friction coefficient because the magnetic layer has a flat and smoothed surface.
Moreover, in the aforementioned magnetic recording medium, as the magnetic powder has a very small size, even if fatty acid is contained in the magnetic layer or used to form a top coat layer, the fatty acid mostly adsorbs to the magnetic powder and, in order to obtain a sufficient effect of the fatty acid, it is necessary to increase the quantity of the fatty acid added. However, if such a great quantity of fatty acid is added, this brings about lowering of the magnetic characteristic of the magnetic layer as well as deterioration of the running condition and durability because the magnetic layer becomes plasticized.